我在Debian 10（buster）和PHP 7.3.19.1以及apache2版本2.4.38和phpmyadmin 5.02中遇到了同样的问题。未解释文件usr/share/phpmyadmin/index.php。在验证了所有手动安装后，我运行了以下命令：

apt-get update
apt-get install libapache2-mod-php7.3
systemctl restart apache2

终于成功了apache2的PHP模块不可用。

sudo apt install php libapache2-mod-php
sudo apt install php7.0-mbstring
sudo a2dismod mpm_event
sudo a2enmod mpm_prefork
service apache2 restart

之后
gedit /etc/apache2/apache2.conf
添加以下行

包含/etc/phpmyadmin/apache.conf

服务apache 2重启

libapache 2-mod-php服务器端，HTML嵌入式脚本语言（Apache 2模块），因此我们必须添加此

在我的情况下，这是由于我安装了apache2后，事实上，然后适当的php mods没有被链接，因此激活。您需要做的是：

cd /etc/apache2/mods-enabled
sudo ln -s ../mods-available/php7.2.conf
sudo ln -s ../mods-available/php7.2.load

然后，您只需通过执行以下命令重新启动服务器：

sudo systemctl restart apache2

如果所有其他PHP页面都工作正常，那么这可能不是PHP相关的问题。
由于只有phpmyadmin登录页面显示php代码而不是实际的登录页面，所以很可能你的apache web根目录/var/www/html/phpmyadmin中的符号链接引用的是phpmyadmin索引文件/usr/share/phpmyadmin/index.php而不是phpmyadmin目录/usr/share/phpmyadmin。
这是一个错误的符号链接：

$ ll /var/www/html
lrwxrwxrwx 1 root root  timestamp  phpmyadmin -> /usr/share/phpmyadmin/index.php

这是一个正确的符号链接：

$ ll /var/www/html
lrwxrwxrwx 1 root root  timestamp  phpmyadmin -> /usr/share/phpmyadmin/

如果符号链接不正确，请更改它：

$ sudo ln -sfn /usr/share/phpmyadmin /var/www/html/phpmyadmin

(Or删除它并重新创建它：）

$ sudo unlink /var/www/html/phpmyadmin
$ sudo ln -s /usr/share/phpmyadmin /var/www/html/phpmyadmin

试试这个

sudo apt-get install libapache2-mod-php7.0

这将安装apache2的库以使用php7.0

请检查下面的东西，已经找到了一些不同的链接给你：

1. Make sure that PHP is installed. This sounds silly, but you never   
    know.

 2. Make sure that the PHP module is listed and uncommented inside of your Apache's httpd.conf This should be something like
    LoadModule    php5_module "c:/php/php5apache2_2.dll" in the file.
    Search for    LoadModule php, and make sure that there is no comment
    (;) in front    of it.

 3. Make sure that the http.conf file has the PHP MIME type in it. This should be something like AddType application/x-httpd-php
    .php.    This tells Apache to run .php files as PHP. Search for
    AddType, and    then make sure there is an entry for PHP, and that
    it is uncommented.

 4. Make sure your file has the .php extension on it, otherwise it will not be executed as PHP.

 5. Make sure you are not using short tags in the PHP file (<?), these are deprecated, and usually disabled. Use <?php instead.
           Actually run your file over said webserver using an URL like http://localhost/file.php not via local access   
    file://localhost/www/file.php

或检查http://php.net/install
谢谢